In semiconductor processing, many operations may be performed on a single workpiece or semiconductor wafer. In general, each processing operation on a workpiece is typically performed in a particular order, wherein each operation waits until completion of a preceding operation, thus affecting the time at which the workpiece will become available for a subsequent processing step. Tool productivity or throughput for relatively short processes performed under vacuum, such as ion implantation, can be severely limited if the process flow leading to the processing location is interrupted by sequential events associated with such processing. For example, operations such as an exchange of workpieces between transport carriers or storage cassettes and the processing system, a transfer of the workpiece from an atmospheric environment into an evacuated environment of an implantation chamber of the processing system, and an orientation of the workpiece (e.g., notch alignment) within the evacuated environment, can have a significant impact on tool productivity.
Processing of a workpiece, such as ion implantation, for example, is typically performed at a reduced pressure within an implantation chamber, wherein ions are generally accelerated along a beam line, and wherein the ions enter the evacuated implantation chamber and strike the workpiece in a predetermined manner (e.g., a predetermined dose, energy, etc.). Several operations are typically performed leading up to the implantation in order to introduce the workpiece into the implantation chamber, as well as to properly position and orient the workpiece with respect to the ion beam within the ion implantation chamber. For example, the workpiece is transferred via a robot from an atmospheric cassette or storage device into a load lock chamber, wherein the load lock chamber is subsequently evacuated in order to bring the workpiece into the vacuum processing environment of the ion implanter. The cassette or storage device, for example, may be delivered to the ion implanter via a conveyor system or other type of delivery apparatus.
As ion implantation processing technology advances, hot ion implantation processes are becoming more common, where a workpiece is heated and implanted with ions at process temperatures ranging from 300° C.-600° C. This process temperature is typically achieved via an electrostatic chuck (ESC) that holds the workpiece during implantation. Such heating via the electrostatic chuck in the vacuum environment of the ion implantation chamber can be time consuming and cause a significant impact to workpiece throughput. Further, when a relatively cold workpiece at room temperature is clamped and heated by an electrostatic chuck to such high process temperatures, thermal expansion of the workpiece can cause deleterious movement of the workpiece with respect to the ESC, causing particles and premature wear of the clamping surface and/or electrodes of the ESC.